The present disclosure relates generally to computer aided design and manufacturing (CAD/CAM) and, more particularly, to a method for modeling, machining, and inspecting complex, three dimensional parts and tool paths through a workpiece.
The cycle of design to machining real parts often takes several weeks to complete and can cost up to several thousands of dollars. In the past, complex tool shapes were generated by hand on a CAD system, which commonly required several iterative steps to get the correct form. The steps might include, design tool e.g., grinder profile and tool path, program the machine for grinding, grind a sample part, and inspect the sample using an inspection apparatus such as a Coordinate Measuring Machine (CMM). This process is repeated until the sample part satisfactorily meets designed requirements and dimensions.
In numerically controlled (NC) milling technology, a tool or cutter is directed through a set of pre-recorded sequential trajectories to fabricate a desired shape from raw stock. This technology is capable of producing free-formed, sculptured surfaces while maintaining tight milling error tolerances. Consequently, NC milling technology is widely used in the production of complicated, high-precision products such as molds, dies, aerospace parts, etc. These products, especially molds and dies, typically influence many other subsequent production processes. In order to improve the accuracy and reliability of NC milling, certain verification methods are used to check milling tool paths for potential problems such as milling error, collision, and improper machining parameters, among others. Analytical methods are implemented to graphically simulate the milling process off-line and, in some cases, verify milling error, tool assembly collision, and other machining parameters. Thus, NC programmers can visualize the shape of milled parts and understand potential problems in an efficient, less expensive, and more accurate way.
Direct solid modeling is one approach used in simulating the material removal process, implemented through direct Boolean difference operations between a solid model of the workpiece and solid models of swept volumes of the milling tool. The milling process may be realistically simulated, resulting in an explicit solid model of the milled workpiece that may be graphically presented and reviewed. Since the milled part is explicitly defined by a solid representation, a subsequent inspection, analysis, and computation of milling error, volume removal rate, or milling dynamics can be readily performed. Although the direct solid modeling approach is theoretically capable of presenting accurate results of NC verification, the applications thereof remain limited. Generally, such limitations result from the complexity of Boolean difference operations between solid entities. The Boolean difference operation requires computation of the intersection between the shells of two solid entities.
Another approach is to represent simple three-dimensional tool shapes (e.g., spheres, cylinders) as a two-dimensional profile that is extruded through a workpiece to provide a real world representation. However, such a simple profile extrusion becomes inapplicable when the tool shape and the tool path are complex. Accordingly, it is desirable to be able to simulate the material removal process for complex tool shapes and paths while overcoming the above limitations.
Additionally, the inspection and analysis of a milled part is generally accomplished with a coordinate measuring machine (CMM), in which a small probe or pointer is used to trace the three-dimensional surfaces of the part in order to measure the specific dimensions thereof. Since such an inspection process assists in decreasing time and expense in the actual manufacturing of parts, it is also desirable to have a similar process for the verification of a mathematical-based, virtual machining application as described above.
Therefore it is desired in the art to provide a method for computer modeling of complex, three dimensional tool paths through a workpiece to facilitate a virtual machining of the workpiece integrated with a process for performing a virtual inspection of a virtually machined workpiece.